Parabolic solar troughs for generating electricity from sunlight energy, include light collector assemblies. Many of these light collector assemblies include a truss frame and a trough-shaped mirror assembly mechanically mounted or attached on the truss frame using threaded studs, washers, and nuts.
FIGS. 2A and 2B collectively show one current method for mechanically attaching the mirror assembly to the truss frame. A ceramic pad 10 is adhesively bonded to the back, non-reflecting surface of a mirror 20 of a mirror assembly. A threaded stud 30 is threadedly engaged in a threaded aperture (not shown) of the ceramic pad 10. The other end of the threaded stud 30 extends through an elongated aperture 44 in a truss frame bracket 42 of a truss frame 40 and a washer 50 and a nut 60 threadedly engaged with the stud 30 at a specified torque, are used to prevent separation of the mirror 20 from the truss frame bracket 42.
Standard mirrors used in the light collector assemblies typically have dimensions about 1700 mm×1500 to 1640 mm, and weigh between about 60 and 80 pounds. A solar thermal plant capable of generating 250 MW of electricity may require over 700,000 mirrors and over 2,800,000 studs, washers, and nuts. Each of these mirrors and their corresponding studs, washers, and nuts must be installed and tighten to the specified torque on site. Often times, the location of these solar thermal plants are in the desert. The cumbersome size and weight of the mirrors make holding the mirrors for alignment of the studs into truss frame apertures a difficult and very time consuming process, and requires a relatively large number of installers. In addition, the installation of the over 2.8 million studs in the ceramic pads and the installation of the over 2.8 million washers and nuts on the studs, stresses the installer's fingers, thus making the installation of the mirrors extremely uncomfortable and difficult. Further, the studs are sometimes cross-threaded into the ceramic pads and/or the nuts are cross-threaded onto the studs. This, in turn, often results in over-torqued nuts on the studs and sometimes, broken studs, which must then be replaced.
Accordingly, there is a need for a new method of mechanically mounting or attaching the mirrors to the truss frame.